High-Resolution Motion-corrected 7.0-T MRI to Derive Morphologic Measures from the Human Cerebellum in Vivo.

Background The human cerebellum has a large, highly folded cortical sheet. Its visualization is important for various disorders, including multiple sclerosis and spinocerebellar ataxias. The derivation of the cerebellar cortical surface in vivo is impeded by its high foliation. Purpose To image the cerebellar cortex, including its foliations and lamination, in less than 20 minutes, reconstruct the cerebellocortical surface, and extract cortical measures with use of motion-corrected, high-spatial-resolution 7.0-T MRI. Materials and Methods In this prospective study, conducted between February 2021 and July 2022, healthy participants underwent an examination with either a 0.19 × 0.19 × 0.5-mm, motion-corrected fast low-angle shot (FLASH) sequence (14.5 minutes) or a whole-cerebellum 0.4 × 0.4 × 0.4-mm, motion-corrected magnetization-prepared 2 rapid gradient-echo (MP2RAGE) sequence (18.5 minutes) at 7.0 T. Four participants underwent an additional FLASH sequence without motion correction. FLASH and MP2RAGE sequences were used to visualize the cerebellar cortical layers, derive cerebellar gray and white matter segmentations, and examine their fidelity. Quantitative measures were compared using repeated-measures analyses of variance or paired tests. Results Nine participants (median age, 36 years [IQR, 25-42 years; range, 21-62 years]; five women) underwent examination with the FLASH sequence. Nine participants (median age, 37 years [IQR, 34-42 years; range, 25-62 years]; five men) underwent examination with the MP2RAGE sequence. A susceptibility difference between the expected location of the granular and molecular cerebellar layers was visually detected in the FLASH data in all participants. The segmentations derived from the whole-cerebellum MP2RAGE sequence showed the characteristic anatomic features of the cerebellum, like the transverse fissures and splitting folds. The cortical surface area (median, 949 cm [IQR, 825-1021 cm]) was 1.8 times larger, and the cortical thickness (median, 0.88 mm [IQR, 0.81-0.93 mm]) was five times thinner than previous in vivo estimates and closer to ex vivo reference data. Conclusion In vivo imaging of the cerebellar cortical layers and surface and derivation of quantitative measures was feasible in a clinically acceptable acquisition time with use of motion-corrected 7.0-T MRI. Published under a CC BY 4.0 license. See also the editorial by Dietrich in this issue.